The objective of this study is to project the introduction of battery-electric and fuel cell technologies into the medium-duty and heavy-duty vehicle markets and to identify which markets will be most suitable for each of technologies and the factors (technical, economic, operational) which will be most critical to their successful introduction. The use of renewable energy sources to generate electricity and produce hydrogen are key considerations of the analysis. The present status of the battery-electric and hydrogen/fuel cell technologies are reviewed in detail and the futures of these technologies are projected. The design and performance of various types of buses and trucks are described based on detailed simulations of the various electrified vehicles. The total cost of ownership (TCO) of each bus/truck type were calculated using EXCEL spreadsheets and their market prospects projected for 2020-2040. It was concluded that before any of the electrified vehicles can be cost competitive with the corresponding diesel powered vehicle, the unit cost of batteries must be $80-100/kWh and the unit cost of the fuel cell system must be $80-100/kW. The long term economics of battery-electric buses and trucks looks more favorable than that for the fuel cell/hydrogen option if the range requirement (miles) for the vehicle can be met using batteries. This is primarily due to the significantly lower energy operating cost ($/mi) using electricity than hydrogen.